1. Field of the Invention
The present invention relates to a serum:plasma separator and a tube for the separation of serum:plasma from clot:hemocyte (referred to as a "blood separation tube" hereinafter). More specifically, it relates to a serum:plasma separator which forms a partition having a medium specific gravity between serum and clot or between plasma and hemocyte when the blood is separated into these two components on the basis of a specific gravity difference, thereby to facilitate the blood separation procedures. The invention also relates to blood separation tube formed by placing the serum:plasma separator in a one end-closed tube and closing the other end of the tube.
2. Description of Related Art
A serum:plasma separator used for conventional blood separation procedures is obtained by incorporating a specific gravity or viscosity adjusting aid such as inorganic fine particles of silica, clay, or the like or an organic gelling agent into a resin selected from a liquid silicone resin, chlorinated polybutene, polyisobutene, an acryl polymer and .alpha.-olefin/maleic acid diester polymer as main components. The resin used as a main component basically has a hydrophobic nature. The inorganic fine particles have an effect in increasing the viscosity of the serum:plasma separator and imparting the serum:plasma separator with a thixotropic nature. The organic gelling agent has an effect in increasing the viscosity of the serum:plasma separator without imparting it with a thixotropic nature.
However, when the above conventional serum:plasma separator is used for centrifugal separation, hemocyte is liable to remain above the serum:plasma separator, i.e., in serum. That is, the separation function of the above conventional serum:plasma separator is insufficient. Further, while centrifugally separated components are stored as they are in place in a separation tube, migration of components having a concentration gradient through the serum:plasma separator takes place between clot and serum or between hemocyte and plasma. Therefore, values obtained by measuring the centrifugally separated and stored blood components, such as potassium ion value, are unreliable.
Meanwhile, the resin as a main component is liquid-like. When a both end-closed tube containing the serum:plasma separator is stored by placing it horizontally, this is unpractical because the serum:plasma separator flows. In order to overcome this effect, a thixotropic aid such as finely milled mica or colloidal silica or an organic gelling agent is incorporated into the serum:plasma separator. The serum:plasma separator containing a thixotropic aid has thixotropic nature at room temperature and is prevented from flowing while it is stored. At a high temperature, however, the thixotropic nature of the serum:plasma separator decreases, and the viscosity of the serum:plasma separator also decreases. Therefore, the separation aid flows. The serum:plasma separator containing an organic gelling agent is prevented from flowing at room temperature and at a high temperature. However, the viscosity of the serum:plasma separator increases with time and the performance as a serum:plasma separator decreases.